The construction
of this barrage began in 1960. The system used consists of a dam 330m long
and a 22km2 basin with a tidal range of 8m, it incorporates a lock
to allow passage for small craft. During construction, two temporary dams were
built on either side of the barrage to ensure that it would be dry, this was
for safety and convenience. The work was completed in 1967 when 24, 5.4m diameter
Bulb turbines, rated at 10MW were connected to the 225kV French Transmission
network.

This
barrage uses Bulb Turbines, which were developed by Electricite
de France. This allows generation on both ebbs of the tide. These axial flow
turbines were also designed to pump water into the basin for the purposes described
earlier. This makes it easier to anticipate generation levels. This type of
turbine is popular with Hydropower and has been used on mainland Europe in dams
on the Rhine and Rhone rivers.

Estimation
on the number of homes this would supply electricity for if a similar system
was set up in Scotland can be found from some simple calculations.

Wave energy
is like most other forms of renewable energy in that it cannot be relied upon
100% of the time so the value quoted above will almost certainly never be generated
in a year. A value of Capacity factor (CF) is used to estimate the
percentage of the maximum that will actually be generated in a year. A capacity
factor of approximately 40% is assumed for Scottish waters.

Electricity
Generated per annum (kWh)
= 2102400000 * 40%

= 840960000 kWh

To estimate
the number of homes that this quantity of electricity will provide for in a
year, the average annual household consumption is used. The average annual household
consumption is assumed to be 4377 kWh/year.

Possible
Future Systems for Tidal Energy: The Stingray

There
are other options for how to extract energy from tidal streams. One example
of a new technology that is stimulating interest at the present time is the
Stingray. This technology consists of a parallel linkage that holds large hydroplanes.
The angle of these hydroplanes to the flow of the tide is varied causing them
to move up and down. This motion is used to extend and detract a cylinder, which
produces high-pressure oil that drives a hydraulic motor that in turn drives
an electric generator.

This
concept has received recognition of its potential from the Department of Trade
and Industry. Firstly, funding for a three-month fast track feasibility study
into the technology was awarded. This lead to the DTI Water and Power Technologies
Advisory Panel supporting the proposal to design, build and install a demonstrator
system in 2002. This system will last for one year and the results will be invaluable
to assessing the Stingrays potential. The support of the DTI is very important,
as it is so difficult to raise money for a technology that has not yet been
demonstrated and proved.

The
Engineering Business (EB) who are developing this technology, did a feasibility
study of potential sites for the deployment of the demonstrator system. They
settled on a site at Yell Sound in Shetland. They are performing an all-encompassing
environmental analysis of the deployment and take into consideration social
considerations and local feelings. The project will be deployed during the summer
of 2002; this will be an important project for tidal stream enthusiasts and
the industry as a whole. If successful, this will be an example to the world
on how to utilise energy from the tides.